Osteoporosis is a serious public health problem faced by an aging US population. Until recently, bone screening was inaccurate and models of fracture risk were relatively crude. A new radiological technique using measurements of the X-ray spectrum can perform several different tests in a single procedure. The complete spectrum of a beam transmitted through two or three different layers of material is collected and areal densities are calculated from the spectral data for each material. The goal of our procedure is to improve the accuracy of in-vivo and patient-specific BMD measurement of Dual-Energy X-ray Absorptiometry (DXA), referred as the "gold standard". Hardening of the two poly-energetic radiation components results in a dependence of in-vivo bone mineral density (BMD) measurements on body size and on weight change and yields an inherent systematic limitation to the sensitivity and accuracy of contemporary planar DXA devices. Our preliminary results suggest that the proposed method of spectral BMD measurement is simple, accurate, beam hardening free, involving low radiation dosage, and is well suited for clinical use. The concept of spectroscopic imaging (DXA-like projection imaging) and a three-material (bone, lean soft tissue, and adipose tissue) decomposition method are included in this proposal. In conjunction with our previously proposed X-ray scattering bone densitometry method, a spectroscopic bone diagnostic device can offer not only an improved measurement of "areal" bone mineral density (BMD in g/cm2), as in conventional DXA but also a QCT-like volumetric BMD (a "true" density in g/cm3) for trabecular bone. Thus, the X-ray spectroscopic method may have a significant impact on national efforts to diagnose, monitor the course of treatment, and to prevent osteoporosis and other metabolic bone diseases. Osteoporosis is a common, silent, and complex disease state of bone that poses a major health threat to our aging population. The disease is characterized by low bone mass, leading to enhanced bone fragility and a significant increase in the risk of fractures, which is typically diagnosed by bone densitometer [1,2]. [unreadable] [unreadable] [unreadable]